Simulations on a potential hybrid and compact attosecond X-ray source based on RF and THz technologies

Abstract

We investigate through beam dynamics simulations the potential of a hybrid layout mixing RF and THz technologies to be a compact X-ray source based on Inverse Compton Scattering (ICS), delivering few femtoseconds to sub-femtosecond pulses. The layout consists of an S-band gun as electron source and a dielectric-loaded circular waveguide driven by a multicycle THz pulse to accelerate and longitudinally compress the bunch, which will then be used to produce X-ray pulses via ICS with an infrared laser pulse. The beam dynamics simulations we performed, from the photocathode up to the ICS point, allows to have an insight in several important physical effects for the proposed scheme and also in the influence on the achievable bunch properties of various parameters of the accelerating and transverse focusing devices. The study presented in this paper leads to a preliminary layout and set of parameters able to deliver at the ICS point, according to our simulations, ultrashort bunches (≈ 1 fs rms), at 15 MeV, with ≥ 1 pC charge and transversely focused down to ≈ 10 µm rms while keeping a compact beamline (≤ 1.5 m), which has not yet been achieved using only conventional RF technologies. Future studies will be devoted to the investigation of several potential ways to improve the achieved bunch properties, to overcome the limitations identified in the current study and to the definition of the technical requirements. This will lead to an updated layout and set of parameters.

Status and objectives of the dedicated accelerator R&D facility “SINBAD” at DESY

“…In parallel to the all optical efforts for THz acceleration in the AXSIS experiments, the linac stage may be tested with the well characterized beam from the ARES linac [20]. In addition to these acceleration experiments, the high frequency of the THz fields will be used in testing THz streaking experiments or bunch length measurements via the 3 phase method [19].…”

Beam dynamics and tolerance studies of the THz-driven electron linac for the AXSIS experiment

“…Our simulations were performed with parameters similar to the planned parameters of the linac and THz-pulse for the AXSIS project [1]. The parameters of the input bunch were taken from [5] and are presented in Table 1. The parameters of the dielectric-loaded accelerator are chosen such that at the cen- tral frequency of the pulse, the phase velocity is exactly equal to the speed of light in vacuum.…”

Preliminary measurements for a sub-femtosecond electron bunch length diagnostic

“…Figure 5 shows a simulation of the reconstruction of such an example electron beam with the combined diagnostic. Here, the initial bunch properties are based on studies by T. Vinatier for accelerating a beam from an S-band RF gun in a dielectric waveguide [17]. The simulation itself was carried out by tracking the initial electron bunch through the diagnostic setup with the code elegant [12] (with visualisation via the elegant implementation of sirepo [13]) and the setup characteristics shown in Table 2.…”